Yeah, I didn’t care for the run flats on my ATS Sedan Premium when I got it. They make what is otherwise an excellent car quite noisy and limit its adhesion. Replaced them with Pilot Super Sports about 500 miles into my ownership. They are amazing on the ATS.
Obviously, the only problem is that there is no spare. That’s what I have roadside assistance for, which is part of the bumper-to-bumper warranty on the vehicle. When the warranty runs out, a good way to get it is through your insurance or, alternatively, via the cheapest OnStar plan.